AMG is rumoured to be testing a V12 with G73 instead of G65. For example, the G63 powertrain is a 4.0-litre V8 bi-turbo Hybrid 800 ps with Motor Assist. The engine is said to rolled out with the G73, S73, and GLS73.
Considering from the price of G65, G73 can be instantly priced high at around 100,000 USD more than G63, it will be much cheaper with a hybrid system. It is a trend worldwide to reduce the emissions to 4.0-litre beginning with China's tax measures, and it is certainly possible.